This reapplication for an NIMH Research Scientist Development Award is designed to prepare the applicant for a career as an independent investigator. To receive the best training opportunities in neuroimmunobiology and molecular biology and to benefit from Dr. Marvin Stein as a mentor, the applicant has changed institutions from Montefiore Hospital to the Mount Sinai School of Medicine. The proposed project focuses on the relationship between the central nervous system (CNS), the endocrine system, and the immune system in patients with Major Depressive Disorder (MDD) and animals subjected a learned helplessness paradigm. Recently, evidence has indicated that lymphocytes from MDD patients exhibit alterations in glucocorticoid receptor (GR) status including decreased sensitivity to in vitro and in vivo steroid challenges and decreased GR numbers. These lymphocyte receptor alterations are relevant for two major reasons. First, altered GR status at the level of the hippocampus, hypothalamus and/or pituitary may underlie abnormalities in the hypothalamic-pituitary-adrenal (HPA) axis in MDD. Altered GR status in lymphocytes may reflect these central receptor abnormalities, providing a basis for using lymphocytes as a potentially important peripheral model system to study HPA axis abnormalities in MDD. Secondly, decreased lymphocyte receptor responsibility to glucocorticoids may provide protection for some MDD patients against the inhibitory immunologic influences of high levels of circulating cortisol. Individuals without such receptor alterations may be immunologically vulnerable to the inhibitory effects of this hormone. The long-term objectives of the proposed research plan are to further evaluate these important neuroendocrine-immune relationships. The specific aims are 1) to determine whether MDD patients with HPA axis abnormalities exhibit alterations in lymphocyte GR status, 2) to determine whether patients with hypercortisolemia and normal lymphocyte GR status exhibit decreases in immune measures, and 3) to determine if there are concurrent GR changes in brain and periphery of learned helpless (LH) animals. To accomplish aims 1 and 2, HPA status, lymphocyte GR status and immune function will be measured in 60 MDD patients and 60 controls. HPA status will be assessed by measuring cortisol secretion over 8 hour period and by conducting a 1 mg DST. Immune measures will include NK Cell activity, mitogen-induced lymphocyte proliferation and the relative numbers of circulating immune cells. Lymphocyte GR status will be determined by measuring Type I and II GR number and lymphocyte sensitivity to an in vitro steroid challenge. Aim 3 will include Type I and II GR assays of cortex, septum, hippocampus and lymphocytes in LH< non-LH and control animals. Intensive training in molecular biology will provide the knowledge to further study steroid receptor ligand binding, activation, translocation into the nucleus, DNA binding, and mRNA transcription.